MSefi.com read only forum (Jan.15,2018)

1985 CRX Si, with MSII board

The CRX voltage regulator is internal, and it apparently is an early example of pcm controlled voltage regulators. Now, no pcm, only MS.

Had it tuned and running before a voltage spike burned out U5.

Anyone have a suggestion for a simple external voltage regulator solution?

Are you saying the alternator was controlled by the original engine ECU? I know some newish cars do this, but didn't know it was around in '85. If so, the easiest way would be to fit a conventional alternator. They're so cheap new it's not worth messing about.

FWIW, MS is pretty well protected from voltage spikes and it would be some spike to destroy U5.

Yup, I didn't think a car that old would have a computer controlled voltage regulator either.

Thanks to Megalog, I know exactly how big the voltage spike was- 25.7. The IC voltage regulator on the board is rated to 26.

Think I can return it for not meeting spec? :>

Some of the Hondas had a simple switched voltage - you grounded the pin that ran to the ECU to make the voltage drop down to around 12 volts; you'd get normal voltage without it. If the ECU had a full-blown voltage regulator in it, though, you could use an external voltage regulator from a different source. A good application to ask for at most parts stores is a '76 Dodge Dart - it has a fairly cheap regulator that works with most externally regulated alternators.

Thanks, Matt. I checked out the Dodge piece. Not only is it cheap and easily available, so is a wiring harness connector for it.